Issues with dtraceasm, and a workaround

[Aleksey Shipilev]

Hi,

On 1/25/21 6:16 PM, Paul Sandoz wrote:
> Sending a TERM signal before destroying the process works around this issue (see patch below). 
> It kicks the dtrace process, resulting in the process relinquishing the remaining dtrace output
> to theoutput file.

This is weird!

> --- a/jmh-core/src/main/java/org/openjdk/jmh/profile/DTraceAsmProfiler.java
> +++ b/jmh-core/src/main/java/org/openjdk/jmh/profile/DTraceAsmProfiler.java
> @@ -87,6 +87,9 @@ public class DTraceAsmProfiler extends AbstractPerfAsmProfiler {
>               throw new IllegalStateException("DTrace needs the forked VM PID, but it is not initialized");
>           }
>   
> +        long dtracePid = dtraceProcess.pid();
> +        Utils.tryWith("sudo", "kill", "-15", Long.toString(dtracePid));
> +
>           Collection<String> messages = Utils.destroy(dtraceProcess);
>           if (!messages.isEmpty()) {
>               throw new IllegalStateException(messages.toString());
> 

Because a few lines below, JMH calls Utils.destroy, which in turns calls java.lang.Process::destroy, 
which in turns calls java.lang.ProcessHandleImpl::destroy(), which in turn calls 
java.lang.ProcessHandleImpl::destroyProcess(/* force = */ false), which calls (I think) 
Java_java_lang_ProcessHandleImpl_destroy0 from ProcessHandleImpl_unix.c, which does deliver SIGTERM:

JNIEXPORT jboolean JNICALL
Java_java_lang_ProcessHandleImpl_destroy0(JNIEnv *env,
                                           jobject obj,
                                           jlong jpid,
                                           jlong startTime,
                                           jboolean force) {
     pid_t pid = (pid_t) jpid;
     int sig = (force == JNI_TRUE) ? SIGKILL : SIGTERM; // <--- here
     jlong start = Java_java_lang_ProcessHandleImpl_isAlive0(env, obj, jpid);

     if (start == startTime || start == 0 || startTime == 0) {
         return (kill(pid, sig) < 0) ? JNI_FALSE : JNI_TRUE;
     } else {
         return JNI_FALSE;
     }
}

...so if we actually deliver KILL not TERM on MacOS, that looks like a JDK bug?

I have no Mac OS nodes to debug this, unfortunately.

-- 
Thanks,
-Aleksey